Software Group
Compilation Technology
Fortran 2003
Jim Xia
IBM Toronto Lab
[email protected]
SCINET compiler workshop | February 17-18, 2009
© 2009 IBM Corporation
Software Group
Compilation Technology
Agenda
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Background
What’s new in Fortran 2003
IBM XL Fortran
Q&A
SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
Background
 50 year anniversary in 2007
 Fortran 2003 published in Nov, 2004
– Fourth edition of Fortran standard
– number of pages increased from 356 (Fortran 95) to 569
– many new features added
– include many interpretations to Fortran 95
– include two Technical Reports
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allocatable dummy arguments and allocatable components
support for IEEE Floating Point Standard (IEEE 1989) (IEEE
intrinsic modules)
 Next revision (Fortran 2008) is near FCD phase
– Publication date is set in 2010
– Major features added: coarrays, submodules
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SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
What’s new in Fortran 2003
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Object-oriented programming support
I/O Enhancements
Scoping and data manipulation enhancements
C interoperability
Procedure enhancements
Parameterized derived type
SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
Object-oriented programming
 type extension (inheritance)
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type fluid
real :: viscosity
real, allocatable :: velocity(:,:,:)
end type
type, extends(fluid) :: magnetofluid
real, allocatable :: magnetic_field(:,:,:)
end type
– type magnetofluid inherited ALL of properties of
fluid: viscosity and velocity
– Only support single-rooted inheritance hierarchy
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SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
Object-oriented programming (cont’d)
 type-bound procedures
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type point
real x, y
contains
procedure :: length => lenBetween2Points
end type
...!definition of lenBetween2Points
real function lenBetween2Points(this, p)
class(point), intent(in) :: this, p
... ! compute the length
end function
...! in main program
type(point) :: pa, pb
...
distance = pa%length(pb)
SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
Object-oriented programming (cont’d)
 Declaration of polymorphic data
– CLASS keyword
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class(fluid) A !could be fluid or magnetofluid
 SELECT TYPE construct
– Allows execution flow controled by dynamic type of the selector
select type(A)
type is (fluid)
... !block for fluid
class is (magnetofluid)
... !block for magnetofluid
class default
...
end select
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SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
Object-oriented programming (cont’d)
 abstract types and deferred binding
– No concrete objects can be declared to have an abstract type
– Deferred binding: defer implementation for type-bound procedures to
extending types, only providing well-defined interfaces
type, abstract :: shape
contains
procedure(shapeArea), deferred :: area
end type
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–
abstract interface
real function shapeArea (this)
import shape
class(shape), intent(in) :: this
–
end function
end interface
SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
I/O enhancements
 user-defined derived-type I/O
– allows user to provide procedures (subroutines) to be used for reading
or writing a derived type
– user defined procedures are invoked by Fortran's READ, WRITE or
PRINT statement as if an intrinsic IO
– useful for derived types with POINTER/ALLOCATABLE components
 stream access I/O
 asynchronous I/O
 Infinities and NaNs in formatted READ and WRITE
– [+/-]INF or [+/-]INFINITY for infinities
– NaN[(...)], for NaNs. e.g. NaN(Q)
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SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
I/O enhancements (cont’d)
 specifier enhancements: allow more control at data transfer
– BLANK= specifier
– PAD= specifier
– DELIM= specifier
 New specifiers for more control
– SIGN= specifier
controls whether the plus sign is displayed for positive numbers in
formatted I/O
– DECIMAL= specifier
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specifies the decimal separator for floating-point number
– ROUND= specifier
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controls the rounding mode for formatted I/O
SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
Data manipulation and scoping enhancements
 allocatable components for derived type
 fine-grained data protection
– private derived type components
 deferred length type parameters:
– character(:), allocatable :: str ! Length of str can be changed at run-time
 array constructors enhancement
– square brackets in array constructors
[ 1, 2, 3 ] is equivalent to (/ 1, 2, 3 /)
– allow type specification
[ real :: 1, 2, 3, 4, 5 ]
 pointer assignment enhancement
– allow lower bounds to be specified for pointer objects
p(0:,0:) => a !p's lower bounds are [0,0]
– remapping of the elements of a rank-one array
p(1:m,1:2*m) => b !b is a rank-one array
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SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
Data manipulation and scoping enhancements (cont’d)
 allow character dummy arguments for MIN, MAX, MINLOC,
MAXLOC, MINVAL and MAXVAL
 access host entities via IMPORT statement in interface block
integer, parameter :: dp = selected_real_kind(15)
!in the same scope of definition of dp
interface
function distribution_function (x) result (res)
IMPORT dp
real(kind = dp), intent(in) :: x
real(kind=dp) res
end function
end interface
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SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
Data manipulation and scoping enhancements (cont’d)
 allocate statement with source-expr
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integer, dimension(4,20) :: arr0
...
allocate(arr1(4,20), source=arr0)
 allocatable array automatic reallocation on assignment
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real, dimension(:,:), allocatable :: A
real :: B(2, 10), C (5, 5), D(5,5)
A = B ! A is automatically allocated as 2 x 10
...
A = C ! A is automatically reallocated as 5 x 5
!reallocation == deallocate -> allocate
A(:,:) = D !NO reallocation here
SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
Data manipulation and scoping enhancements (cont’d)
 rename operators on USE statement
use a_mod, operator (.plus.) => operator (.add.)
 PROTECTED module data
module temperature_mod
real, protected :: temperature
contains
subroutine set_temperature (temp)
real, intent(in) :: temp
temperature = temp
end subroutine
end module
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SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
C interoperability
 provide a standardized mechanism for interoperating with C
 intrinsic module ISO_C_BINDING – contains named constant
holding kind type parameter values for intrinsic types
type
integer
...
real
named constant
C_INT
C type or types
int
C_FLOAT
C_DOUBLE
float
double
 provide facilities of interoperability with C data, pointers, struct, and
procedures
– Interop with C global data variables
real(C_FLOAT),dimension(100),bind(C,name='Alpha')::alpha
bound to
float
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Alpha[100];
SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
C interoperability (cont'd)
– Interop with C struct
type, BIND(C) :: point
real(C_FLOAT) :: x, y
end type
interoperable with
typedef struct{
float x1, x2;
} point_t;
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SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
C interoperability (cont'd)
– Interop with C procedure and procedure interfaces
interface
subroutine sub (i, r) bind(C, name='proc')
integer(C_INT), VALUE :: i
real(C_DOUBLE) r
end subroutine
end interface
Fortran interface interoperable with C prototype
void proc (int, double *);
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Call sub in Fortran resolves to an invocation on a procedure
named “proc”
SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
More C interoperability
 enumerations
enum, bind(C)
enumerator :: two=2, five=5
enumerator :: six
end enum
declares an enumerator with constants 2, 5 and 6
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SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
Procedure enhancements
 VALUE attribute on dummy argument
– call by value
 abstract interface
– declares a procedure interface without declaring an actual procedure
 declare procedures using procedure interface name (prototype)
procedure(problem_solver) :: forward_euler, backward_euler
 procedure pointer
procedure(problem_solver), pointer :: solution
solution => forward_euler
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SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
Parameterized derived types
 derived type allowed to have KIND and LENGTH type parameters
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integer, parameter::dp = selected_real_kind(15)
type matrix(kind,m,n)
integer, kind :: kind=dp
integer, len :: m, n
real(kind) :: element(m,n)
end type
type(matrix(dp,10,20)) :: a
declares a double-precision matrix of size 10 x 20
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type(matrix(dp, :, :)), allocatable :: mat
...
ALLOCATE (matrix(dp, m, n) :: mat)
size of matrix mat is determined at runtime
SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
IBM XL Fortran
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standard compliance is one of the XL compiler priorities
IBM actively participates in the standard development
implement Fortran 2003 features since V8.1 (GA 2002)
V12.1 contains all Fortran 2003 features except parameterized
derived types
– First OO Fortran compiler in the industry
 V12.1 supports most OpenMP3.0 features
 implemented features are available on all supported platforms
 for more information, please visit
http://www-01.ibm.com/software/awdtools/fortran/
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SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation
Software Group
Compilation Technology
Q&A
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SCINET compiler workshop | Fortran 2003
© 2009 IBM Corporation